<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>


        var a = 10;
        var b = 20;

        // 交换变量的值
        // 错误示范
        // b = a; 
        // a = b;


        // 正确示范
        // var temp = b;
        // b = a;
        // a = temp;
        // console.log(a,b);

    </script>
</body>

</html>